A “pars” usually refers to the pars interarticularis , a small segment of bone in the back part of a vertebra that connects different joints of the spine. It sits between the upper and lower facet joints of a vertebra and helps link the front and back parts of the spinal column so the spine can move while staying stable. Stress fractures in this area are called “pars fractures” or “pars defects” and are a common cause of lower back pain in young athletes.
